<template>
    <div class="app-container">
        <el-tree
        :data="data"
        show-checkbox
        default-expand-all
        node-key="id"
        ref="tree"
        highlight-current
        :props="defaultProps">
        </el-tree>

        <div class="buttons">
        <el-button @click="getCheckedNodes">通过 node 获取</el-button>
        <el-button @click="getCheckedKeys">通过 key 获取</el-button>
        <el-button @click="setCheckedNodes">通过 node 设置</el-button>
        <el-button @click="setCheckedKeys">通过 key 设置</el-button>
        <el-button @click="resetChecked">清空</el-button>
        </div>
    </div>
</template>

<script>
export default {
 methods: {
      getCheckedNodes() {},
      getCheckedKeys() {},
      setCheckedNodes() {
        this.$refs.tree.setCheckedNodes([{
          id: 5,
          label: '二级 2-1'
        }, {
          id: 9,
          label: '三级 1-1-1'
        }]);
      },
      setCheckedKeys() {
        this.$refs.tree.setCheckedKeys([3]);
      },
      resetChecked() {
        this.$refs.tree.setCheckedKeys([]);
      }
    },

    data() {
      return {
        data: [{
          id: 1,
          label: '一级 1',
          children: [{
            id: 4,
            label: '二级 1-1',
          }]
        }, {
          id: 2,
          label: '一级 2',
          children: [{
            id: 5,
            label: '二级 2-1'
          }, {
            id: 6,
            label: '二级 2-2'
          }]
        }, {
          id: 3,
          label: '一级 3',
          children: [{
            id: 7,
            label: '二级 3-1'
          }, {
            id: 8,
            label: '二级 3-2'
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    }
}
</script>

<style>

</style>
